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The local properties of the dispersed gas phase (gasholdup, bubble diamater, and bubble velocity) were measured and evaluated at different positions in the riser and downcomer of a pilot plant reactor and, for comparison, in a laboratory reactor. These were described in Parts I and II of this series of articles during yeast cultivation and with model media. In the riser of the pilot plant reactor, the local gas holdup and bubble velocities varied only slightly in axial direction. The gas holdup increased considerably, while the bubble velocity increased only slightly with aeration rate. The bubble size diminished with increasing distance from the aerator in the riser, since the primary bubble size was larger than the equilibrium bubble size. In the downcomer, the mean bubble size was smaller than in the riser. The mean bubble size varied only slightly, the bubble velocity was accelerated, and the gas holdup decreased from top to bottom in the downcomer. In pilot plant at constant aeration rate, the properties of the dispersed phase were nearly constant during the batch cultivation, i.e., they depended only slightly on the cell concentration. In the laboratory reactor, the mean bubble sizes were much larger than in the pilot plant reactor. In the laboratory reactor, the bubble velocities in the riser and downcomer increased, and the mean gas holdup and bubble diameter in the downcomer remained constant as the aeration rate was increased.

Saccharomyces cerevisiae was cultivated in a 4-m(3) pilot plant airlift tower loop reactor with a draft tube in batch and continuous operations and for comparison in a laboratory airlift tower loop reactor of 0.08 m(3) volume. The reactors were characterized during and after the cultivation by measuring the distributions of the residence times of the gas phase with pseudostochastic tracer signals and mass spectrometer and by evaluating the mixing in the liquid phase with a pulse-shaped volatile tracer signal and mass spectrometer as a detector. The mean residence times and the intensities of the axial mixing in the riser and downcomer, the circulation times of the gas phase, and the fraction of the recirculated gas phase were evaluated and compared.

In 1987, 12 years after fluoridation of drinking water, caries prevalence of Prague school-children is very low, and the goals of WHO have already been reached and undercut. Children from Rostock, where no fluoridation of drinking water was introduced, have an unchanged high caries experience in 1985. Degree of treatment and percentage of successfully treated children show only little differences in both towns. These results emphasize the demand for an introduction and/or a continuation of an effective caries prevention in children once more.

Using oral plaque-pH-telemetry the cariogenic potential of a sucrose-solution (10%), a sorbitol-solution (10%), of a roll with honey, a roll with jam together with sweetened coffee and the "Milchschnitte" has been examined. All sugar containing products cause a deep pH-drop in dental plaque. The duration of demineralization (time of plaque-pH below 5.5)-amounts to 75 min. after mouthrinsing with sucrose-solution, 80 min. after consuming a half roll with honey, 140 min. after eating a roll with jam and drinking sweetened coffee and 82 min. after consuming a "Milchschnitte". All these products shouldn't be used as in-between-meals or snacks without a consequent oral hygiene afterwards.

The results of a cross-sectional study of caries prevalence in 22,112 children age 6 to 14 years in Rostock Country are classified as moderate to high according to WHO criterions. Territorial differences in the caries prevalence have a strong connection to the degree of realisation of preventive measures. Over a control period of 20 years the average caries experience in children showed only little changes, a general caries decline couldn't be watched.

Using CPITN recommended from the WHO periodontal treatment needs in 22,118 children between 6 and 14 years from Rostock County were estimated. According to that the need of periodontal care in the examined young population is low and preventive care has precedence. For children until 12 years of age the evaluation of CPITN has some problems. The routine application of the CPITN is recommended as a screening for high-risk patients.

In relation to the goals for oral health by the year 2000 a detailed territorial analysis of caries prevalence in 12 years-old children in performed. There from a prognosis of the future caries development in this age group considering regional conditions is given.

The authors represent a further program-system for computer aided data processing of the results from the systematic dental examinations in children. The data input starts with the summarized dates of each class fixed in the sumlist (printed form 2008). This program needs less computer capacity and considers the limited availability of personal computers in dentistry for children.

Saliva of 95 patients of different ages was investigated for S-IgA and free secretory component (SC). The two-directional rocket method was used as assay for separating S-IgA and free SC in the presence of heparin-Ca-EDTA. The method employs electrophoresis in an antibody containing agarose/agar gel.--The value of S-IgA in children about 4 years old was 40,0 mg/l and the relation of free SC to S-IgA was 1 to 5. The S-IgA level in patients over 50 years old was 55,2 mg/l, in no case free SC was detectable.

In continuation of the program of data recording presented earlier a computer program for analysis and calculation of a data base which consists of the results of dental examination of children is introduced. The presented possibilities of data processing are fitted to the general reports in dentistry of children. They are recommended in solving the problems of a simple and modern data processing in this special field of dentistry.